When rotors of wind turbines are mounted on a hub, they have an emergency system for switching off the rotor or the wind turbine if there is an overspeed or a too large difference between generator high speed and generator low speed.
Conventional systems of a wind turbine have a redundant over speed detection system, which is able to trig an emergency safety system. An overspeed controller comprises a slave module for measuring the overspeed and a Main Computer (MC) for detecting the overspeed. The limit is a parameter in the main controller, and the sensor is an inductive sensor. A controller over speed, as it is called, trigs the hydraulic emergency system by activating a “Safety Switch”. The slave modules in the hub are able to break the safety circuit, but this feature is only used if a communication error at a CAN BUS in the system is detected, or if they are restarted by a watch-dog internal in the slave modules.
Conventional systems comprises further a Low speed Monitoring Unit (LMU) for monitoring the LS (low speed)-speed, and triggering the hydraulic emergency system by hard wired emergency circuit if the limits are exceeded. The LMU outputs a speed feedback to the main computer, which is supervised to insure that the LMU is in operation. Conventional systems comprise furthermore A High Speed (HS) Centrifugal Unit (HCU) for triggering the hard wired emergency circuit if the limit is exceeded. Further, a Speed Sensor Error may be detected by to large differences between generator HS speed and generator LS speed.
There may be a need for providing a system providing a cost effective approach for triggering an emergency system of a wind turbine.